Many different wearable rubber parts exist for use in fluid handling services. Such wearable rubber parts provide various functions in, for example, the transport of fluid. Wearable rubber parts can be used to control the flow of fluid, provide passages for fluid flow, and connect together adjoining segments of a passage system, to name just a few examples. Specific examples of wearable rubber parts used in fluid handling services include, but are not limited to, expansion joints, pinch valves, and hoses.
Expansion joints are generally used in rigid piping systems to compensate for axial, lateral, torsional and/or angular movement and misalignment due to, for example, thermal expansion and contraction, mechanical effects, system settlement, pressure surges or changes, and system vibrations.
Pinch valves are a type of control valve that use a pinching effect to control fluid flow. When a pinch valve is open, fluid generally flows freely through the pinch valve. When a pinch valve is closed, the pinching effect obstructs fluid flow. Pinch valves are often used in systems where slurries or fluids with entrained solids are the conveyed media because the flexible rubber sleeve of a pinch valve allows the valve to close droptight around solids.
Hoses are generally hollow cylindrical passages that can be used to convey fluids over various distances. Hoses are often flexible in nature to provide some measure of freedom in arranging the hose around or over obstructions and the like. Hoses can also be designed to absorb system vibration, compensate for thermal expansion and contraction, and reduce noise.
Many previously known wearable rubber parts use certain limited elastomers as a component of the rubber part. For example, certain types of elastomers are commonly used as the inner most layer of wearable rubber parts. In addition to providing the degree of flexibility typically needed in wearable rubber parts for fluid handling services, elastomers have typically been used due to their low cost and abrasion resistance.
However, the abrasion resistance of these certain types of elastomers is less than ideal. For example, some media, such as fluids with a high amount of entrained solid particulate, will degrade the elastomers over a relatively short period of time, such that wearable rubber parts need to be replaced frequently. This decreased service life increases costs and maintenance downtime.
Because conventional elastomers generally do not have sufficient abrasion resistance for use in some highly abrasive applications, efforts have been undertaken to identify alternative materials for use as the inner most layer of wearable rubber parts. One material having higher abrasion resistance than certain types of elastomers is polyurethane. However, polyurethane has not been used as an inner most layer in wearable rubber parts because of numerous issues that would arise from the use of polyurethane.
One particular issue with the use of polyurethane as an inner most layer is that polyurethane is difficult to process into the shape needed for an inner most layer of a wearable rubber part. The viscosity of polyurethane is generally high, which makes it difficult to calendar the material into the desired shape.
Another issue is that the industry generally regards polyurethane as not having sufficient water resistance for use as an inner most layer of a wearable rubber part.
Issues also arise with respect to adhering polyurethane inner most layers to adjacent layers in the wearable rubber part composite structure. In order to provide a useful wearable rubber part, the bond between the polyurethane inner most layer and the adjacent layer must be both strong enough to resist delamination and flexible enough to permit the degree of movement required in wearable rubber parts for fluid handling. Typical adhesives are incapable of providing both of these characteristics. For example, a typical cement-like adhesive can provide the necessary bond between the polyurethane inner most layer and an adjacent layer, but the dried adhesive is brittle and therefore does not provide the required flexibility.
Due to at least one or more of the above identified issues, polyurethane has been rejected by the industry for use as an inner most layer of a wearable rubber part. However, if some or all of the problems identified above could be resolved, the use of polyurethane as an inner most layer of a wearable rubber part would be useful due to its good abrasion resistance characteristics and suitability for use in highly abrasive applications where.